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Author
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Topic: Another PCV question... Alex?
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grandestang
Gearhead Posts: 375
From: Lake Bluff, Illinois USA
Registered: Jan 2003
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posted 01-03-2005 10:24 PM
 
Okay I was under the impression that the PCV system was actually good for the engine because the slight vaccuum created by it in the crankcase... thus improving piston ring seal. However it was recently brought to my attention that the vacuum pulled by the PCV is so little (less than 1 PSI) that it makes no difference. Another argument is the fact that a PCV will keep your oil cleaner. But I've seen breathers on a car with the car revving and I can noticeably see gasses emmitted from the breathers... they seem to be doing their job. I just don't see any advantage of running the PCV, if it doesn't pull enough vaccuum to affect anything than it seems like I'm just getting my intake all gunked up with oil for nothing. This is critical on my 98 4.6 DOHC becasue it has an Intake Runner Manifold Control system that opens up a secondary port in the intake above 3250 rpm and this system is prone to getting gunked up with oil over time. I used to think it was a good thing to have but now I am doubting it and may pull it in favor of breathers. So can anyone give me a good argument of why to leave it on? (Besides the enviromental reasoning). Alex I remember you once brought up some very good points on why it was good to run a PCV, but I was not able to find them in the search. Paul ------------------
1970 Grande
H code 351W FMX 1998 SVT Mustang Cobra
Bright Atlantic Blue http://mustangsandmore.50megs.com/MembersPics/grandestang.html
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trashline
Gearhead Posts: 2230
From: Levittown, Pa
Registered: Dec 2003
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posted 01-03-2005 11:20 PM
im not alex but. my pcv port pulls about 19 inches of Hg. vacuum isnt described in psi . psi is for pressure. inches of Hg can be used as pressure and vacuum. the atmosphere can be measured in inches of Hg. anywho enough chemistry class for today. it allows any fumes that got into the crankcase to be burned off. if you put a breather on it will then gunk up your valve cover with road grime. on the outside. the biggest thing is for emissions i think. sorry i couldnt give you a better answer im sure alex will come along------------------
1966 mustang coupe
200ci, 3.03 3 speed tranny
holley weber two barrel conversion, msd 6a ignition, blaster 2 coil, pertronix, 2 inch exhaust to a glass pac, stock rear (3.20),ram air install complete (homemade)
white w/ black interior, soon be painted antique bronze with the R model apron and gt350 hood scoop (functional)
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grandestang
Gearhead Posts: 375
From: Lake Bluff, Illinois USA
Registered: Jan 2003
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posted 01-03-2005 11:34 PM
1 PSI=2.036"Hg (inches of mercury), so I guess it just depends on the type of measurement you are using.Paul
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Moneymaker
Administrator Posts: 29200
From: Lyons, IL, USA
Registered: May 99
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posted 01-04-2005 01:05 AM
Low tension oil rings will promote combustion chamber oil vapor contamination.
A good PVC system will help evacuate the crank case and hinder the contamination.------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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grandestang
Gearhead Posts: 375
From: Lake Bluff, Illinois USA
Registered: Jan 2003
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posted 01-04-2005 10:11 PM
So in other words with 3000 mile oil changes the PCV is not really necessary?I just don't see the point of it. The fact that it gets my intake so full of crud, makes it not sensible to continue running it. Unless there is something I'm missing here. Paul ------------------
1970 Grande
H code 351W FMX 1998 SVT Mustang Cobra
Bright Atlantic Blue http://mustangsandmore.50megs.com/MembersPics/grandestang.html
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69 Sportsroof
Gearhead Posts: 2814
From: Valley, Alabama, USA
Registered: Mar 2002
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posted 01-04-2005 10:26 PM
What exactly do you mean by sludge? You should only get a very light oil vapor through your pcv. This will make a slight brownish colored stain inside the intake without any buildup. Do your valve covers have metal baffles in them? The rubber ones just wont do the job. Have you checked to make sure you pcv valve is working properly? If its stuck open then you can get a steady draw of vapor instead of a controlled amount.
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Moneymaker
Administrator Posts: 29200
From: Lyons, IL, USA
Registered: May 99
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posted 01-04-2005 10:31 PM
quote:
Originally posted by grandestang:
So in other words with 3000 mile oil changes the PCV is not really necessary?I just don't see the point of it. The fact that it gets my intake so full of crud, makes it not sensible to continue running it. Unless there is something I'm missing here. Paul
It depends on the oil you are using along with how efficiant a ring seal you have.
You have nothing to gain by eliminating the PCV. ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA & SS/MA National Record Holder '00,'01,'02,'03,& '04
First SS/MA in the TENS!
IHRA division 5 Superstock Champion
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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trashline
Gearhead Posts: 2230
From: Levittown, Pa
Registered: Dec 2003
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posted 01-04-2005 10:50 PM
lol you dont hear to often people refering to vacuum in terms of psi thats more what i was pointing to.still im not big wig but theres no gains to removing it. ------------------
1966 mustang coupe
200ci, 3.03 3 speed tranny
holley weber two barrel conversion, msd 6a ignition, blaster 2 coil, pertronix, 2 inch exhaust to a glass pac, stock rear (3.20),ram air install complete (homemade)
white w/ black interior, soon be painted antique bronze with the R model apron and gt350 hood scoop (functional)
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grandestang
Gearhead Posts: 375
From: Lake Bluff, Illinois USA
Registered: Jan 2003
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posted 01-05-2005 01:11 AM
As I said in my first post, this is about my 98 Cobra. This particular year (96-98s) 32V 4.6 had an Intake Manifold Runner Control system which is basically a butterfly flap that opens up a second port above 3250 rpm. So kinda like the old 4V Clevelands, these engines love high revs. The problem is there is no fuel injector in the second port opening so the second port and butterfly flap over time become coated with oil which can gunk up and impair the system from working smoothly. Scroll down and look through the pictures in this link and you can see what I'm talking about with this IMRC system.
http://www.svtmustangcobraclub.com/media/pdfs/tech/IMRC_Cleaning.pdf
Apparently cleaning IMRCs on these engines is a common thing to do, but it just seems like all this trouble could be avoided if I went the breather route. So I dunno, maybe there is something to gain by gettin rid of them. Paul ------------------
1970 Grande
H code 351W FMX 1998 SVT Mustang Cobra
Bright Atlantic Blue http://mustangsandmore.50megs.com/MembersPics/grandestang.html
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